The brain performs the most complex and essential processes in the human body. Surprisingly, contemporary health care lacks sophisticated tools to objectively assess brain function at the point-of-care. A patient's mental and neurological status is typically assessed by an interview and a subjective physical exam. Clinical laboratories currently have no capacity to assess brain function or pathology, contributing little more than identification of poisons, toxins, or drugs that may have externally impacted the central nervous system (CNS).
Brain imaging studies, such as computed tomography (CT) and magnetic resonance imaging (MRI) are widely used to visualize the structure of the brain. However, CT scan and MRI are anatomical tests and reveal very little information about brain function. For example, intoxication, concussion, active seizure, metabolic encephalopathy, infections, and numerous other conditions (e.g. diabetic coma) show no abnormality on CT scan. A classical stroke, or a traumatic brain injury (TBI), may not be immediately visible in an imaging test even if there is a clear and noticeably abnormal brain function. Similarly, diffuse axonal injury (DAI), related to shearing of nerve fibers which is present in a majority of concussive brain injury cases, can remain invisible on most routine structural images. If undetected at an early stage, swelling or edema from DAI can subsequently lead to coma and death.
Functional MRI (fMRI) is a recent improvement over MRI, which provides relative images of the concentration of oxygenated hemoglobin in various parts of the brain. While the concentration of oxygenated hemoglobin is a useful indication of the metabolic function of specific brain regions, it provides very limited or no information about the underlying brain function, i.e., the processing of information by the brain, which is electrochemical in nature.
Further, CT and MRI/fMRI testing devices are not field-deployable due to their size, power requirements and cost. These assessment tools play an important role in selected cases, but they are not universally available, require experienced personnel to operate, and they do not provide critical information at the early stages of acute neurological conditions. Current technologies are unable to provide the immediate information critical to timely intervention, appropriate triage, or the formulation of an appropriate plan of care for acute brain trauma. Unfortunately, the brain has very limited capacity for repair, and thus time-sensitive triage and intervention is very important in treating brain injuries.
Currently, emergency room patients with altered mental status, acute neuropathy, or head trauma must undergo costly and time-consuming tests to determine an appropriate course of treatment. Unfortunately, in many cases, the clinical condition of patients continue to deteriorate as they wait for equipment to become available or for specialists to interpret tests. The problem that faces ER physicians is that their resources are limited to a subjective physical exam using a flashlight and a reflex hammer, and all of the physician's decisions concerning the administration of emergency treatment, additional consultation by a neurologist, or patient discharge, are based on the results of this simplistic exam. Often, ER patients are sent for imaging studies, yet many functional brain abnormalities, as discussed earlier, are not visible on a CT scan or MRI. Some abnormalities which eventually have anatomical and structural consequences often take time to become visible on an imaging test. This is true for many important conditions, such as ischemic stroke, concussion, raised intracranial pressure, and others. This indicates the need for real-time, functional brain state assessment technology, which can be performed in the ER, or in an ambulatory setting, and can detect emergency neurological conditions hours ahead of the standard clinical assessment tools available today.
All of the brain's activities, whether sensory, cognitive, emotional, autonomic, or motor function, is electrical in nature. Through a series of electrochemical reactions, mediated by molecules called neurotransmitters, electrical potentials are generated and transmitted throughout the brain, traveling continuously between and among the myriad of neurons. This activity establishes the basic electrical signatures of the electroencephalogram (EEG) and creates identifiable frequencies which have a basis in anatomic structure and function. Understanding these basic rhythms and their significance makes it possible to characterize the electrical brain signals as being within or beyond normal limits. At this basic level, the electrical signals serve as a signature for both normal and abnormal brain function. Just as an abnormal electrocardiogram (ECG) pattern is a strong indication of a particular heart pathology, an abnormal brain wave pattern is a strong indication of a particular brain pathology.
Even though EEG-based neurometric technology is accepted today in neurodiagnostics, its application in the clinical environment is notably limited. Some of the barriers limiting its adoption include: the cost of EEG equipment, the need for a skilled technician to administer the test, the time it takes to conduct the test, and the need for expert interpretation of the raw data. More importantly, the lack of portability of this technology makes it infeasible for point-of-care applications. A fully-equipped diagnostic EEG instrument typically costs around $80,000. Despite the high costs, the instrument produces essentially raw waveforms which must be carefully interpreted by an expert. Moreover, use of the standard EEG equipment remains extremely cumbersome. It can take 30 minutes or more to apply the required 19 electrodes. Once a subject is prepared for the test, the EEG recording can take from 1 to 4 hours. Data is collected and analyzed by an EEG technician, and is then presented to a neurologist for interpretation and clinical assessment. This makes the currently available EEG equipment inadequate for neuro-triage applications in emergency rooms or at other point-of-care settings. Thus, there is an immediate need for a portable brain state assessment technology to provide rapid neurological evaluation and treatment guidance for patients with acute brain injury or disease, so as to prevent further brain damage and disability. Additionally, there is a need for objective quantification of brain functionality in order to enable clinicians, EMTs or ER personnel, who are not well trained in neurodiagnostics, to easily interpret and draw diagnostic inferences from the recorded data. This in turn will help the medical personnel in selecting an immediate course of action, prioritizing patients for imaging, or determining if immediate referral to a neurologist or neurosurgeon is required.